DESCRIPTIONS OF THE LARVAE OF FOUR NORTH PACIFIC 

 PORCELLANIDAE (CRUSTACEA: ANOMURA)' 



S. L. Conor and J. J. Gonor^ 



ABSTRACT 



Complete descriptions are given of the zoea and megalopa stages of four porcelain crabs 

 common in the rocky intertidal regions of the Pacific coast of North America. Both 

 larvae reared in the laboratory and larvae taken from the plankton were available for 

 the species Petrolisthes cinctipes (Randall), Petrolisthefs eriomerus Stimpson, Pachy- 

 cheles pubescens Holmes, and Pachycheles rudis Stimpson. All four species have a short 

 prezoea stage, two zoeae, and a planktonic megalopa stage. Extensive variation was found 

 in setal numbers between left and right members of appendage pairs and between indi- 

 viduals in these larvae. Setal counts characteristics of species cannot be obtained from 

 one or a few larvae, and ranges in the counts overlap considerably between species. 

 The criteria of Lebour for grouping zoeal types in the Porcellanidae are applied to these 

 four species and comparisons made between all available descriptions of porcellanid 

 larvae. Intermolt growth of appendage buds occur in these four species, and it is con- 

 cluded that this type of growth is the cause of most of the differences described previously 

 as larval substages. Tabulations of species showing stage variation and intermolt growth 

 are given. 



All larval stages of four common Pacific coast 

 rocky intertidal porcelain crabs have been reared 

 in this laboratory. Material obtained from cul- 

 tures and from the plankton was used for the 

 descriptions given here of the larvae of each 

 species. One of these species, Pachycheles rudis, 

 has been described previously (Knight, 1966), 

 and in this case the available material permitted 

 this description to be expanded. Attention was 

 also directed to variation in larval characteris- 

 tics since adequate numbers of specimens were 

 available for examination. 



Gravid female porcelain crabs of the species 

 Petrolisthes cinctipes (Randall), Petrolisthes 

 eriomerus Stimpson, Pachycheles rudis Stimp- 

 son, and Pachycheles pubescens Holmes were 



' Research supported in part by a traineeship from 

 Crant Nos. 5T1-WP-111-02, -03, and -04, Federal Wate>- 

 Quality Administration, and by National Oceanic and 

 Atmospheric Administration (maintained by the U.S. 

 Department of Commerce) Institutional Sea Grant 

 2-35187. 



^ Department of Oceanography and Marine Science 

 Center, Oregon State University, Newport, OR 97365. 



Manuscript accepted January 1972. 



FISHERY BULLETIN: VOL. 71, NO. 1, 1973. 



collected from rocky intertidal shores at Boiler 

 Bay and Yaquina Head on the central Oregon 

 coast. P. rudis was collected from the lower 

 intertidal ( — 0.8 to — 2.5 ft below mean lower 

 low water) beneath Phyllospadix root mats on 

 the seaward sides of large boulders. Pachycheles 

 pubescens was collected from burrows and crev- 

 ices in rock at the same tide level. The Petrol- 

 isthes species were gathered somewhat higher 

 in the intertidal regions of the two sites beneath 

 loosely bedded rocks and rubble. All four spe- 

 cies occur in various other habitats as well 

 (Haig, 1960) but were taken from these areas 

 for convenience. Egg-carrying Pachycheles 

 rudis were collected in May and June of 1968. 

 In the same months of 1969, egg-bearing females 

 of the other species were obtained for larval 

 studies. Gravid females were also noted dur- 

 ing other months of the year, in agreement with 

 Knudsen's (1964) observations on the repro- 

 ductive cycles of these species. The specific 

 identity of the females used was confirmed by 

 comparing them to the descriptions given by 

 Haig (1690). 



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